What defines a single characteristic or fact about an entity?

The concept of an attribute is fundamental in systems analysis and design as it specifies a single characteristic or fact about an entity in a data model. An entity represents a distinct object within the system—for example, a customer or product—while attributes provide relevant details about these entities. For instance, if we consider a customer entity, attributes might include the customer’s name, address, and phone number.

Attributes serve as properties that describe entities, making it easier for analysts and developers to understand the relationships between different components of the system. This ensures that data is accurately represented and helps in organizing information within the database. In this context, the term 'attribute' is more precise and widely recognized than the alternatives listed.

Other terms, while related, do not specifically define a characteristic about an entity. A property can refer to the inherent characteristics of an object but lacks the specificity of attributes in the context of data modeling. A feature typically refers to a broader capability or functionality, not a singular characteristic. Lastly, a variable is a broader term often used in programming or mathematics, and does not specify its association with entities in systems design. Thus, the choice of attribute accurately fits the definition provided in the question.